SDT's Vigilant Allows for Close Monitoring of Wind Farms

Ontario is powered by renewable, clean energy wind farmers, which can have lengthy life expectancy free of trouble if they are forewarned of critical component failure.

Image Credit: SDT Ultrasound Solutions

Yet, wind turbines present unique challenges for condition monitoring technicians as they are complex assets consisting of both slow and high-speed components. With safety training and advanced technologies, these challenges can be overcome.

The height where data must be collected is one such challenge. Wind turbines in the United States have an average height of 280’ (85.3 m). This poses significant safety and accessibility concerns for condition monitoring technicians.

The logistical nightmare when failed or failing components need replacing or maintaining is another challenge reliability technicians must overcome.

In both instances, expensive heavy-duty machinery with trained operators for multiple down days is required. This means that the best way to minimize cost overruns or to mitigate them all together is planning these interventions weeks or months in advance.

The differing rotational speeds of a wind turbine’s components is the third challenge that condition monitoring technicians face. Vibration analysis works well for monitoring assets that rotate fast, such as the drive end and non-drive end bearings on the main generator.

The turbine’s slow rotating components are where vibration falters. The generator’s bearings turn much faster than the main bearing on a wind turbine.

Slow-speed bearings create insufficient vibration, making them ineffective as monitoring tools. Thus, condition monitoring technicians put their trust in ultrasound technology to monitor slow-rotating assets.

Accessibility

The height at which condition monitoring technicians must perform their data collection is the most glaring accessibility challenge they face. Technicians must complete a mandatory eight-plus hour Working at Heights safety training course before even ascending a wind turbine.

The element of employee safety requires consideration whenever working at extreme heights. For technicians working on turbines without lifts, this is especially true. There is an extra element of fatigue for technicians climbing 50-100 meters up a ladder, especially if they are required to make this ascent multiple times in a single day.

Additionally, it uses up a technician’s valuable time to have to repeatedly ascend and descend wind turbines all day. As time becomes scarce, companionship becomes a sensible consideration.

A permanent condition monitoring solution that streams data to a wind farm’s maintenance headquarters is ideal for extreme heights. The need for frequent trips up and down a wind turbine is reduced, and the reliability of the department’s operation and overall efficiency of maintenance is improved.

Forewarning of Critical Component Failure

Maintenance crews must act swiftly to restore operation to the turbine when critical components inside the nacelle fail. It is an expensive and difficult challenge to replace and repair large components at extreme heights.

For performing this maintenance on wind turbines, skilled labor and heavy-duty cranes are necessary. The cost and headache of coordinating these maintenance efforts are reduced by finding faults and predicting impending failures far in advance.

The D-I-P-F curve is a common model outlining the typical life of an asset. Ultrasound technology owns the APEX of the D-I-P-F curve, as shown in the following diagram.

The largest window of opportunity for corrective repair is provided by ultrasound as it detects impending and potential failures earlier than vibration, infrared or any other condition monitoring technology.

Image Credit: SDT Ultrasound Solutions

Inside the Nacelle

Reliability and maintenance technicians can perform their job better and more efficiently by choosing the right condition monitoring technology. A wind turbine’s critical components are depicted by looking inside the nacelle.

The turbine blades are connected to the rest of the mechanism by the main bearing. Depending on wind speeds, this main turbine shaft turns around 10-20 rotations per minute. The non-drive end, the generator drive end and the turbine’s gearbox turn much faster than the slow-speed main shaft.

Image Credit: SDT Ultrasound Solutions

Success Story

Matt Jeffrey, Mark Nanni and Robert Dent - all SDT Ultrasound Solutions representatives - recently installed the first Vigilant System on a 90-meter-tall wind turbine in Southwestern Ontario.

Vigilant is a permanent solution for condition monitoring with both vibration and ultrasound analysis capabilities. Inputs from eight data sources can be managed continuously by each Vigilant pod (no multi-plexing is necessary).

Condition monitoring data streams to its onboard trending and analysis application live, via cellular, ethernet or WIFI. A constant diet of information about the health of their remote and critical assets is fed to reliability teams.

Analysts of any skill level will be able to easily access complex analysis tools normally reserved for expensive, high-end vibration software. There are also no tricky licensing setups because the application is web-based. Users only need to log in with their favorite browser to start analyzing.

The turbines’ critical components were already being permanently monitored using vibration analysis. Vigilant was deployed to use ultrasounds to monitor seven key data collection points.

One data collection point was put on both the drive-end and non-drive-end of the turbine’s generator, one was on the slow-speed main bearing, and four were on the gearbox.

The turbine turns 91 times slower than the bearings on the main generator, which means ultrasound is optimal for monitoring the slow-speed main bearing.

Ultrasound warns users of changes to safe, normal operating parameters and reveals imminent failures as it is receptive to micro-sonic changes in low energy events caused by friction and impacts.

All key data collection points now benefit from a more complete analysis with Vigilant installed through smart data from both vibration and ultrasound.

The installation was completed very quickly by SDT personnel, and condition monitoring data was streaming from the Vigilant System 90 meters in the air to the wind farm’s maintenance office in just under two hours.

Analysis

SDT

Image Credit: SDT Ultrasound Solutions

Planetary Bearing – the ultrasound reading confirmed the presence of impacting, as expected from the initial vibration data.

Slow-Speed Main Bearing – Higher than expected ultrasound reading with lots of impacting came back from the initial reading on the main bearing. Lubricating the bearing was SDT’s recommendation.

SDT

Image Credit: SDT Ultrasound Solutions

Afterward, ultrasound decibel levels dropped, indicating a reduction in both impacting and friction, which is visible in the figure below.

Slow-Speed Main Bearing, Before and After Greasing

Slow-Speed Main Bearing, Before and After Greasing. Image Credit: SDT Ultrasound Solutions

SDT

Image Credit: SDT Ultrasound Solutions

SDT

Image Credit: SDT Ultrasound Solutions

The main bearing had additional analysis conducted on it. It was discovered that there were repetitive impacts at a BPFO of approximately 13.5 times the running speed, which is consistent with an outer race defect.

The recommendation from SDT was to closely monitor the main bearing’s condition. Eventually, the main bearing will need to be replaced because of the defect.

Installing the Vigilant System benefitted the wind turbine maintenance by granting seven permanent ultrasound data collection points on the critical components of their wind turbine. They were able to confirm a suspected defect on the planetary bearing using their new data, which was originally detected using vibration analysis.

A new defect on the main bearing that went undetected by the vibration sensors already in place was also found. The technicians noticed a significant drop in friction levels after applying some grease to the main bearing. Moving forward, the technicians will continue to monitor the main bearing closely.

This information has been sourced, reviewed and adapted from materials provided by SDT Ultrasound Solutions.

For more information on this source, please visit SDT Ultrasound Solutions.

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